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Thread: caster wheels

  1. #11
    Quote Originally Posted by brian View Post
    Nonoise - that's a pretty cool setup and I imagine weight distribution has a lot to do with stability. The caster is out so far forward there's little weight on it.



    Four wheels are inherently more stable than three. Three might be fine at slow speeds or on smooth or flat surfaces (like a tennis court), but I wouldn't want to take three outside on uneven pavement and in any kind of hurry. going straight would be okay, but watch out in turns.

    If three wheels were as stable as four, all cars would have three wheels to save on costs. A few car companies have tried it. Polaris has the Slingshot and Elio Motors has it's car, but they hve two in front and one in back for stability in turns.

    As an example of why you want two wheels in front, there's the Relinat Robin:

    I've used my highly modified three wheel Shadow chair outdoors for over four years on uneven pavement or off trail, straight or turns, not worrying about speed too much. As you point out the long wheelbase is important, but also is my 8 inch pneumatic caster. Another is that I straightened the steering axle to perpendicular from the original. I suspect by design even the Freewheel's is not perpendicular. I have not had one incident of front tipping in those four years and I have taken it in places most all wheelchairs cannot go. Also it rolls faster than I can get other chairs up to since that wheel never shimmies. Here is a youtube we made for another purpose. It does not show how versatile this chair is since it was done at a childrens park, but it's what I've got.
    https://youtu.be/p9nYkKIm-uo

    Also as for the Reliant Robin episode, check out this video rebuttal confession. He rigged it to flip.
    http://www.independent.co.uk/arts-en...-a6810016.html
    Last edited by nonoise; 01-23-2018 at 10:40 PM.
    I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.

  2. #12
    Senior Member brian's Avatar
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    Why would television lie to me?


    I know this sin't exactly the same, but I broke a plastic caster while on vacation by running into a broken curb cut the wrong way. The impact just ripped through all three spokes and the wheel dangled freely on the hub (I now only use solid machined aluminum caster wheels). Missing a caster, of course, made my chair really unstable. I had to be very careful about not leaning forward at all.

    Therefore, I have a slightly irrational aversion to any three wheeled vehicle/chair design.

  3. #13
    Senior Member sowseng's Avatar
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    Quote Originally Posted by nonoise View Post
    I took an old Shadow tennis chair and modified it for an everyday chair. I changed it to have zero camber, and an eight inch pneumatic caster mounted Freewheel style. I also changed the underseat crossmember to allow the smartdrive battery clearance.

    Lately I have had to finish the project with footrests and anti tippers. It has never been sideways tippy, I don't know why, it just is not. The rigors of a tennis court might be different. But the smart drive clone caused too much acceleration, so I added the anti tips.

    This chair is unbelievably fast, easy to push. It rolls if the brakes are not set. I've transferred into the barber chair and the barber unlocked the brakes and moved the chair to the other side of the room. It then rolled back on it's own. Boy was he surprised, I chuckled.
    I like what you have modified.
    Life is meaningles, though you create the purpose.

  4. #14
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    it was a bearing it just went inside the wheel danged if the other did the same thing a week later so I got my old one on

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